1. Field of the Invention
The present invention relates to a light source device used for a picture display device or the like, and more particularly to a light source device that synthesizes laser beams emitted from a plurality of semiconductor laser devices and concentrates the beams into an optical fiber in order to obtain a predetermined light output.
2. Description of the Related Art
A conventional light source device, which synthesizes laser beams emitted from a plurality of semiconductor laser devices and concentrates the beams into an optical fiber, in order to obtain a predetermined light output, is configured to include: a plurality of chip-like semiconductor lasers arranged and fixed on a heat block; collimator lens arrays provided corresponding to the semiconductor lasers; a condenser lens that concentrates collimator light flux generated by the collimator lens arrays into one optical fiber; and a box-like package that air-tightly seals these multiplexing optical systems.
According to the light source device of this kind, to concentrate laser beams emitted from the semiconductor laser devices into an optical fiber, the semiconductor laser devices, the collimator lens arrays, the condenser lens, and the optical fiber must be fixed with a predetermined positional precision in a state that inclinations of these parts precisely match with each other. To fix these parts in this manner, there is proposed a structure in which inclinations of precisely formed parts are measured by a laser automatic collimator and in this state, these parts are positioned precisely by a mechanical hand and are adhered and fixed (see, for example, Japanese Patent Application Laid-open No. 2006-284851 (Page 7 and FIG. 1)).
When a semiconductor laser device having an emission wavelength in a range of 350 to 450 nanometers is used, organic gas (out gas) components of e.g., an adhesive for fixing multiplexing optical systems are deposited on a light emitting unit and an optical member, and this deteriorates laser characteristics. To solve this problem, there is proposed a light source device in which the concentration of organic gas in a package is limited to less than 1000 parts per million (ppm), and inert gas having an oxygen concentration in a range of 1 to 100 ppm is enclosed into the package (see, for example, Japanese Patent No. 4115732 (Page 5 and FIG. 2)).
According to the conventional light source devices, parts such as a semiconductor laser device, a collimator lens array, a condenser lens, and an optical fiber are individually adjusted in position and assembled while measuring inclinations thereof. It is necessary to perform positioning operations many times for each semiconductor laser device, and thus there is a problem that the operability in assembling is not good.
Further, because an adhesive is interposed between joint surfaces of these parts, there is a possibility that a positioned part is deviated when the adhesive is cured. Therefore, it is necessary to form each part extremely precisely and the device become expensive, yet there is a problem that positional deviation or optical deviation (inclination of optical axis and aberration) between the laser device and a lens cannot be optimally adjusted, and the coupling efficiency is deteriorated. Further, when an ultraviolet cure adhesive is used, one of parts that are to be bonded must have ultraviolet permeability, and thus materials used for the parts are limited.
It is also necessary to air-tightly seal the optical system, to manage the concentration of organic gas in a package, and to enclose inert gas in the package. Therefore, there is a problem that the device becomes more expensive and the operability in assembling is deteriorated, and thus the device cannot be easily applied to inexpensive consumer devices.
The present invention has been achieved in view of the above problems, and an object of the present invention is to provide a light source device capable of easily and precisely adjusting positions of optical axes of a semiconductor laser device and a lens.